Yann Trolez

High-yield formation of substituted tetracyanobutadienes from reaction of ynamides with tetracyanoethylene.

A high-yielding sequence of [2+2] cycloaddition-retroelectrocyclization of ynamides with tetracyanoethylene (TCNE) is described. The reaction provided tetracyanobutadiene (TCBD) species, which were characterized by various techniques. DFT and TD-DFT calculations were also performed to complement experimental findings.

Straightforward Synthesis of 5‐Bromopenta‐2,4‐diynenitrile and Its Reactivity Towards Terminal Alkynes: A Direct Access to Diene and Benzofulvene Scaffolds

The high-yielding synthesis of 5-bromopenta-2,4-diynenitrile (BrC5 N) was achieved for the first time. Its reactivity with triisopropylsilylacetylene and triisopropylsilylbutadiyne in the presence of copper and palladium as co-catalysts and diisopropylamine was evaluated. It revealed an unprecedented cascade reaction leading to a diene in one case and to a benzofulvene in the other case, with a unique structure. Both of them were characterized by X-ray crystallography, among other techniques. The mechanism of the reaction leading to the diene was investigated experimentally. Theoretical calculations at the DFT level suggest that the mechanism leading to the benzofulvene relies on a hexa-dehydro Diels-Alder (HDDA)-type of mechanism. This work constitutes an example of an unanticipated reactivity leading to an important increase of chemical complexity.

Methylcyanobutadiyne: synthesis, X-ray structure and photochemistry; towards an explanation of its formation in the interstellar medium.

Out of this world: A new convenient synthesis of methylcyanobutadiyne (see figure), an interstellar compound, is described. It was characterized by various techniques including X-ray structure determination. Photolysis experiments were carried out on binary gaseous mixtures of interstellar relevant compounds to understand how methylcyanobutadiyne could be formed in the interstellar medium.

Gas-Phase Infrared Spectroscopy of Substituted Cyanobutadiynes: Roles of the Bromine Atom and Methyl Group as Substituents.

The IR spectra of 5-bromo-2,4-pentadiynenitrile (Br-C≡C-C≡C-CN) and 2,4-hexadiynenitrile (CH3 -C≡C-C≡C-CN), a compound of interstellar interest, have been recorded within the 4000-500 cm(-1) spectral region and calculated by means of high-level ab initio and density functional calculations. Although the calculated structures of both compounds are rather similar, there are very subtle differences, mainly in the strength of the C≡C bond not directly bound to the substituent. These subtle bonding differences are reflected in small, but not negligible, differences in the electron density at the corresponding bond critical points, and, more importantly, are reflected in the IR spectra. Indeed, the IR spectrum for the bromine derivative presents two well-differentiated strong bands around 2250 cm(-1) , whereas for the methyl derivative both absorptions coalesce in a single band. These bands correspond in both cases to the coupling between C≡C and C≡N stretching displacements. A third, very weak, band also associated with C≡C and C≡N coupled stretches is observed for the bromine derivative, but not for the methyl one, owing to its extremely low intensity.

Reactivity of functionalized ynamides with tetracyanoethylene: scope, limitations and optoelectronic properties of the adducts

The reactivity of functionalized ynamides and arylynamines with tetracyanoethylene at room temperature was evaluated. In most cases, the corresponding 1,1,4,4-tetracyanobutadienes (TCBDs) were obtained in good to excellent yields through a [2+2]-cycloaddition/[2+2]-retro-electrocyclization sequence. The influence of diverse functional groups on the yield of the reaction was investigated, in particular concerning multiple ynamides. These TCBDs were characterized by various spectroscopic techniques and electrochemistry and X-ray diffraction in some cases.

Rotational spectrum of 4-methylcyanoallene (CH3CH=C=CH-CN), a chiral molecule of potential astrochemical interest

Context. A successful identification of an interstellar compound requires that its spectrum has first been assigned in the laboratory. New and sensitive radiotelescopes, such as ALMA, will make it possible to detect interstellar molecules in much smaller concentrations than before. Cyanoallene (CH2=C=CH-CN) has recently been observed in the dense molecular cloud TMC-1 by means of its rotational spectrum. Its methyl congener, 4-methylcyanoallene (CH3CH=C=CH-CN), may also be present in the interstellar medium (ISM). This chiral compound exists in two forms, which are mirror images. Chirality is an essential feature of life. So far, no chiral compounds have been detected in the ISM. Aims. The synthesis and assignment of the rotational spectrum of CH3CH=C=CH-CN, will facilitate the potential detection of this compound in the ISM. Methods. The spectrum of 4-methylcyanoallene has been recorded between 13 and 116 GHz using the microwave spectrometer at the University of Oslo. The spectroscopic study has been augmented with high-level quantum chemical calculations at the B3LYP/cc-pVTZ and CCSD/cc-pVTZ levels of theory. Results. The rotational spectra of CH3CH=C=CH-CN in the ground vibrational state and in the first vibrationally excited state are reported for the first time and accurate spectroscopic constants have been obtained from a large number of transitions.

Infrared and Raman spectroscopy of methylcyanodiacetylene (CH3C5N)

A spectroscopic study combining IR absorption and Raman scattering is presented for methylcyanodiacetylene (CH3 C5 N). Gas-phase, cryogenic matrix-isolated, and pure solid-phase substance was analyzed. Out of 16 normal vibrational modes, 14 were directly observed. The analysis of the spectra was assisted by quantum chemical calculations of vibrational frequencies, IR absorption intensities, and Raman scattering activities at density functional theory and ab initio levels. Previous assignments of gas-phase IR absorption bands were revisited and extended.

Helicenes Grafted with 1,1,4,4-Tetracyanobutadiene Moieties: π-Helical Push-Pull Systems with Strong Electronic Circular Dichroism and Two-Photon Absorption

Enantiopure P- and M-carbo[6]helicenes substituted with one or two tetracyanobutadiene moieties at positions 2 and 15 have been prepared. Grafting of these electron-accepting groups onto the π-helical core resulted in strong charge-transfer effects, which greatly affected the UV/Vis, electronic circular dichroism (ECD), and two-photon absorption (TPA) responses. The ECD signal was found to be reversibly switched by applying a redox stimulus.

One-step synthesis of conjugated enynenitriles from bromocyanoacetylene

The chemical reactivity of bromocyanoacetylene has been evaluated for the first time by making it react with terminal alkynes and secondary amines in the presence of bis(triphenylphosphine)palladium dichloride and copper iodide as co-catalysts. This reaction provides new conjugated enynenitriles stereoselectively in one step in variable yields.